Former RCR Tomlinson boss Paul Dalgleish claims he acted honestly when running the engineering group before it collapsed a year ago in his defence of a lawsuit alleging he misled investors who were left with worthless shares after the company was liquidated.

The class action lawsuit has been filed in the NSW Supreme Court and is being led by Quinn Emanuel Urquhart & Sullivan after three separate actions were combined. It alleges RCR did not disclose losses from its solar farm projects until after they materialised with "devastating consequences" for shareholders.